The present invention relates to topically applicable compositions useful and particularly effective for treatment of dermatological lesions and prevention of other adverse effects of microorganism growth on skin.
Dermatological lesions, including acne, seborrhea, tinea (ringworm) infections, tinea cruris (jock itch), tinea pedis (athletes' foot) and reaction to plant contactants such as the oleoresins of poison ivy, are prevalent medical problems.
Acne and seborrhea are human skin conditions characterized by an excessive flow of sebum (skin oil) from the sebaceous glands located in the pilosebaceous apparatus. Sebum travels through hair follicle ducts to the skin surface. Excessive sebum in or near these ducts may act to block the flow of sebum to the skin surface. Such blocking in turn may produce a thickening and solidification of the sebum to form a solid plug termed a comedone. Comedone formation may stimulate hyperkeratinigation of the hair follicle openings to induce even further blockage or complete closure of the ducts. As a result of this blockage, papules, pustules or cysts may result and are often contaminated with bacteria, whose proliferations cause secondary infections. Acne, and seborrhea to a lesser extent, are particularly characterized by the presence of comedones, inflammatory papules, pustoles or cysts. The suppression or elimination of these secondary bacterial infections will result in a return to sound dermatological health. Many treatments have been tested to achieve the elimination of these secondary dermatological infections and their too frequent results of dermatological and/or psychological scarring. No treatments thusfar tested have solved this medical problem in a generally satisfactory manner.
Various fungi, often termed dermatophytes, are able to colonize areas of the skin resulting in irritating, or even disfiguring and infectious dermatological lesions. The suppression and elimination of these dermatophyte infections such as ringworm, athletes foot, and jock itch have also been an object of the medical profession.
Exposure of many individuals to allergenic plants such as poison ivy may result in dermatological lesions such as painful and irritating skin rashes. The prevention and alleviation of such plant-induced rashes is another long-standing object of the medical profession.
Microbes present on the skin, particularly when allowed to proliferate in moist skin areas, are thought to be causes of objectionable body odor. The prevention of such objectionable body odor in those susceptible thereto is a well-established desire of many people.
Benzoyl peroxide, (C.sub.6 H.sub.5 CO).sub.2 O.sub.2 (BZP), is a potent nontoxic oxidant which has long been used for treatment of dermatological lesions and known to be an effective anti-microbial and anti-keratolytic agent useful, for example, in the treatment of acne. Difficulties noted with BZP preparations have included BZP chemical instability. In its particulate solid form BZP has been found to be generally more stable than its dissolved form. However, when a preparation containing BZP particles is utilized to treat dermatological lesions, the BZP particles eventually contacting the skin may have adverse irritative effects. These adverse effects appear to result, at least in part, from the excessive concentrations of BZP at skin areas in contact with BZP particles. Methods of avoiding such adverse effects while still effectively utilizing BZP therapeutically are long-sought. Therapeutic preparations comprising BZP particles and glycerol have been commonly utilized. Glycerol is generally acknowledged not be a solvent for BZP, but to be a soothing emollient for skin.
Certain prior attempts to create stable, pharmaceutically effective and dermatologically non-irritative BZP preparations have involved the production of minute BZP crystals. For example, U.S. Pat. No. 4,401,835, issued to Tarasoy, describes a method of preparing BZP crystals ranging below ten microns in size. The procedure of U.S. Pat. No. 4,401,835 was described as comprising: (1) preparing a first solution comprising BZP and a "precipitate promoting material." (The "precipitate promoting material" was a solvent for BZP preferably able to produce a solution containing up to about 15% by weight BZP. In the preferred embodiment the "precipitate promoting material is the dimethyl ether of 1,4:3,6-dianhydrosorbitol (dimethyl isosorbide) or tetrahydrothiophene-1,1-dioxide); (2) adding (preferably slowly with vigorous agitation) the first solution to a second solution wherein the BZP precipitates as a fine crystalline dispersion. (The second solution comprised an aqueous solution of a non-toxic dispersant which was non-reactive with BZP. This dispersant was a cellulose derivative or a surfactant (non-ionic or anionic)); and (3) recovering the five BZP crystals (which may be washed if desired or used directly).
Even very fine BZP crystals are, of course, still finite particles. Such particles may contact the skin and generate high BZP concentrations at such points of contract.
One object of the present invention is to minimize or avoid the contact of BZP particles with the skin of an individual being treated with a BZP preparation.
A further object of the present invention is a BZP preparation which is stable and, after application to the skin of an individual, results in the contact of a BZP solution with the skin areas being treated.